Many tools have been made to facilitate the measurement and/or cutting or scoring of a piece of sheet rock to a desired size for use in the construction of building walls and ceilings.
For example, U.S. Pat. No. 5,197,195 to Aikens describes a cutting guide apparatus having an elongate handle containing a magazine housing including a reel of flexible measuring tape extending through a guide plate that is adjacent a distal end of the handle. A collet member permits selective extension of the measuring tape and the forward distal end of the flexible measuring tape includes a support beam including a mount for a writing instrument and a cutting tool therein. However, the flexible nature of the measuring tape does not permit a rigid member to insure an accurate marking/scoring/cutting by a mounted writing instrument or cutting tool. This is especially relevant at greater extensions of the flexible tape from the handle and increases the difficulty of its use.
U.S. Pat. No. 5,265,342 to Lang describes a drywall measuring and cutting tool having a guide riding the edge of a sheet of drywall and a rigid, graduated rod passing through an opening in the guide and normal thereto. A knife is fastened to the rod by a stem assembly and the stem assembly can be rotated for shallow or deep cuts. However, the idle rod length projects away from the knife through the guide which requires a minimum free space behind the sheet of drywall, especially for cuts closer to the guide. Additionally, the rod is selectively fixed within the guide by a downward pressure of the handle of the guide towards the rod which tends to lift the knife end away from the drywall and increases the difficulty in manipulating the device to cut or score the sheet of drywall. Also, since the depth of the score/cut is determined by rotation of the stem assembly, the user must exert a constant and consistent downward pressure on the handle of the stem assembly to ensure a consistent depth of scoring/cutting. This further complicates use of the device.
U.S. Pat. No. 2,818,644 to Crawford describes a wallboard measuring and cutting device having a sliding stop member with a flat, rigid, elongated calibrated rod passing through an opening in the stop member and normal thereto. Secured to one end of the rod is a block member which extends transversely to the rod. The block member includes a cutting blade perpendicular to the rod and selectively positioned to score or cut a sheet of drywall or the like. The opposite end of the rod includes a depending stop block which prevents removal of the sliding stop member. In use, the sliding stop member is selectively positioned along the calibrated rod at a specified distance from the cutting blade as read by the markings on the rod and is fixed in position by a pivoting arm having a curved bottom which frictionally engages the rod. The sliding stop member projects below the plane of the bottom of the calibrated rod and includes an edge which abuts the edge of a sheet of drywall. The device is guided along the edge of the drywall scoring/cutting the drywall at the specified distance. However, as in Lang, the idle rod length projects away from the block member/cutting blade which requires a minimum free space behind the sheet of drywall, especially for cuts closer to the sliding stop member.
U.S. Pat. No. 3,286,351 to McAlister describes a sheetrock scriber which scribes, or scores, a piece of sheetrock, or the like, at a predetermined distance so that the sheetrock can be accurately broken off to the desired size. The sheetrock scriber having a carriage riding over a piece of sheetrock on a set of tandem rollers on one end and a single roller positioned on a scriber head member at the other end of a ruler arm extending from the carriage. The tandem rollers are spaced and journaled on a vertically extending leg and are journaled on individual axles. The vertically extending leg has an edge with beveled lips angling outwardly to facilitate abutment of the leg with an edge of the sheetrock. The ruler arm may be suitably graduated to allow measured placement of a scriber blade within the scriber head member at the desired distance from the edge of the vertically extending leg. The scriber head member is selectively positioned along the ruler arm by squeezing of a lever member against the scriber head member to clamp the ruler arm at the desired distance. The scriber blade projects below the single roller at a predetermined fixed distance to ensure proper scribing of the sheetrock.
However, similar to Lang and Crawford, the idle ruler arm length projects away from the vertically extending leg which requires a minimum free space behind the sheetrock, especially for cuts closer to the vertically extending leg. Further, the rollers upon which the carriage/ruler arm rides over the sheetrock are subject to binding upon embedding of pieces of scribed sheetrock and dust in their axles/sleeves produced during use of the device. This could lead to necessary periodic cleaning of the roller members and difficulty in the efficient use of the device due to difficult scribes and may lead to binding or jumping of the device creating nonlinear scribes and therefore nonlinear breaking of the sheetrock.
U.S. Pat. No. 4,644,663 to Needs describes a measuring device to locate, dimension and mark the proper locations for the successive formations of score lines in a plurality of multi-sided conduits or ducts formed from planar sheets of duct board without having to reset the device each time a separate duct board is marked. The measuring device being in the form a T-square having a rigid, elongated body and a perpendicularly arranged head portion and further including a plurality of staggered, offset scales extending along the length of the body in adjacent, side-by-side and parallel relation to one another from the head portion towards a distal end. A plurality of scale indicators, preferably equal in number to the number of scales, are positioned to slide along the length of the body in aligned indicating relation with one of the plurality of scales. Each scale indicator includes a locking member to selectively lock each scale indicator relative to its respective scale. Each scale indicator further includes a marker member extending outwardly therefrom and positioned to allow markings to be made on the product being measured by the device by each scale indicator marker member as determined by the locked position of the scale indicator relative to the measurement indicia on its respective scale. The device is intended to allow for accurate multiple V-shaped scorings of successive duct boards so that each scored duct board may be folded upon itself along the score lines to form multiple, identical substantially rectangularly-shaped ducts or conduits that may then be affixed to each other end-to-end to create, most commonly, air conditioning ducts. Each V-shaped score line has a definite width which must be accounted for to allow proper placement of the next and successive score lines to allow formation of the selected sized duct. The scales are staggered a predetermined amount relative to each other to account for the V-shaped score line width.
In use, the device is set so that the side-by-side scales are offset an appropriate amount for the size of the duct to be formed and the marker members are locked at the desired positions. Marks are made at each marker member at either end of the duct boards and a straight edge is used to connect the pairs of marks made by the device to indicate along the entire appropriate dimension of the duct board where the V-shaped score lines are to be cut by a separate tool. The Needs device is not designed to make continuous score lines to cuts but is instead designed to account for the width of the V-shaped score lines, to be subsequently produced by a separate tool, necessary to form rectangular-shaped ducts from the duct boards. Further, the device is not compact and is of a fixed length creating an unnecessarily bulky and unwieldy device for simple scoring or cutting of a sheet of material to a single desired width.
U.S. Pat. No. 4,949,462 to Spencer describes a drywall cutting device that includes a channel-shaped sleeve for slidably mounted disposition on a stem of a T-square at predetermined selectable positions. A handle operated clamping device consisting of a screw inserted in a threaded hole in the sleeve that may be rotated so that the screw's distal end engages the stem of the T-square is provided to selectively position the sleeve on the stem. The sleeve further includes a knife holder within which a knife is positioned perpendicular to the stem for cutting a line perpendicular to the stem when the clamping device and the T-square are drawn together across a surface to be cut. The stem may include graduated indicia to establish the measured distance from the knife edge to the edge of the T-square engaging the edge of the sheet of the material to be cut. As with Needs, McAlister, Crawford, and Lang, the device is not compact but instead is of a fixed length creating an unnecessarily bulky and unwieldy device.
U.S. Pat. No. 4,799,315 to Ziegler describes a knife support and cutting guide for a type of cutting tool commonly used to cut paperboard as a border for framing pictures. The device having a two piece clamp at the end of a curved arm for holding the cutting tool while the other end of the curved arm has a first circular member which mates with a corresponding second circular member on the end of an elongated rod to selectively maintain the curved arm at a predetermined rotational orientation relative to the elongated rod by the use of a screw, for example. One of two interchangeable, surface engaging guide members is releasably retained at a desired position along the length of the rod permitting the cutting tool to make either a circular or a straight cut in the paperboard with a beveled edge. The rotational adjustment of the two circular members permits alignment of the cutting tool edge when making circular cuts to eliminate blade drag. The elongated rod is selectively slidingly engaged to the surface engaging guide members through a hole therein to allow for selective adjustment of the distance from the cutting tool to the chosen surface engaging guide member. To make straight cuts, a flat edged surface engaging guide member is chosen to produce a T-square shaped device with the elongated rod perpendicularly attached to the flat edge member. The flat edge member abuts the edge of the material to be cut and the flat edge member and cutting tool is drawn along the edge of that material to cut the material at a predetermined distance from its edge.
As with Needs, McAlister, Crawford, Lang, and Spencer, the Ziegler device is not compact but instead is of a fixed length creating an unnecessarily bulky and unwieldy device. Further, the device is of a relatively flimsy construction for cutting sheet rock over prolonged periods and is not provided with calibrated indicia to permit rapid and accurate measured scoring or cutting. None of the prior art patents disclose a compact sheet rock scoring/cutting device that is useful over the range of measured distances for common sheet rock.
Accordingly, it is an object of this invention to provide a sheet rock cutting tool that is compact while extendible to allow cutting of standard sizes of sheet rock.
Another object of the present invention is to provide a tool that permits measuring and scoring or cutting sheet rock in a single motion.
Other objects will appear hereinafter.